The results show that a warm high ridge at the middle level and transformed surface cold high over the plain provide a good background condition ; a cooling process produced by net surface radiation fluxes is the trigger and strengthening mechanism for the fog event ; the subsidence flow at the middle and low tropospheric levels is favorable for the setting - up and maintenance of stable stratification at the boundary layer and weak wind condition at the ground layer over the fog region ; the transportation of weak warm advection at lower levels and weak lift motion at the boundary layer play a very important role to the long maintenance of the fog event ; the intrusion of north wind accompanied by cold advection is a main dynamic factor of the fog dissipation 结果表明：在中高层暖性高压脊及地面变性冷高压稳定维持的大尺度背景条件下，地表净辐射引起的近地层冷却是大雾过程的触发和加强机制；中低空下沉气流的存在有助于近地层的弱风条件和稳定层结的建立；低层暖平流的输入和边界层的浅层抬升是大雾长时间持续的原因；伴随冷空气南下的偏北大风是驱使大雾消散的动力因子。
